X-ray diagnostic apparatuses, including a rotary-anode type X-ray tube, sometimes have three rotation modes, i.e., a stopped state, a low rotating speed, and a high rotating speed. For example, in the case of the low rotating speed, the X-ray diagnostic apparatus may emit X-rays in a fluoroscopy mode and in an acquiring mode with a low radiation dose. In the case of the high rotating speed, the X-ray diagnostic apparatus may emit X-rays in a fluoroscopy mode, in an acquiring mode with a low radiation dose, and in an acquiring mode with a high radiation dose.
However, the X-ray diagnostic apparatus needs time to increase the rotating speed of the anode from the stopped state or the low rotating speed to the high rotating speed. Furthermore, if the X-ray tube emits X-rays in such a state that the rotating speed of the anode is insufficient, there is a possibility that the anode is melted due to the heat that is caused by electron collision. Therefore, conventional X-ray diagnostic apparatuses start to acquire fluoroscopic images and acquisition images with delay.